@total_ordering
class A(object):
    def __init__(self, value):
        self.value = value
    def __lt__(self, other):
        if not isinstance(other, A):
            return NotImplemented
        return self.value < other.value
    def __eq__(self, other):
        if not isinstance(other, A):
            return NotImplemented
        return self.value == other.value

@total_ordering
class C(object):
    def __init__(self, value):
        self.value = value
    def __lt__(self, other):
        if not isinstance(other, C):
            return NotImplemented
        return self.value < other.value
    def __eq__(self, other):
        if not isinstance(other, C):
            return NotImplemented
        return self.value == other.value

# This works as expected:
print(A(2)<A(3)) # True
print(A(2)>A(3)) # False
# Comparing A and C, however, causes a stack overflow:
print(A(2)<C(3))